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Q: "Can I put a <insert engine here> into my <insert Subaru here>?"A: Subaru has a high interchangability rate as far as drivetrain components go. If your car came with an EJ series engine, then any other EJ series engine will "drop" into your chassis. I say "drop" because while they do share the same engine mounts, some other components may be required to change first before the engine can go in. Think Legos.

Q: "What is an 'EJ' series engine?"A: EJ is the engine code for many Subaru engines. It is thought to have the following definition: E-Engine and J-H4. They are commonly found in the Impreza, Legacy, Liberty (overseas Legacy), Forester, and WRX. The typical naming convention is the engine code followed by the engine size. ie: a 1.8L engine from a 1993 Subaru Impreza is EJ18.

Q: "I have <insert subaru here>, what are my swap options?"A: Lets go over the model history first:
EJ18: Found in Imprezas from 1993-1997. Rated at 110hp and 120 ft-lbs
EJ22 Phase I: Found in Legacies from 1990-1998 and Imprezas from 1995-1998. Comes rated at 130hp and 137 ft-lbs, 135hp and 140 ft-lbs, or 137hp and 145 ft-lbs.
EJ22 Phase II: Found in Legacies in 1999 and Imprezas from 1999-2001. Rated at 142hp and 149 ft-lbs.
EJ22-T Phase I: Found in Sport Sedan and Touring Wagons (Legacies) from 1990-1994. Turbocharged and non-intercooled. Rated at 160hp and 181 ft-lbs. Closed deck, cast pistons, forged rods, oil squirters: turbo motor. Poor flowing heads.
EJ25 DOHC Phase I: Found in Legacies from 1996-1999, Imprezas in 1998, and Foresters in 1998. Rated at either 155hp and 140 ft-lbs in 1996 or 165hp and 162 ft-lbs in 1997-1999.EJ25 SOHC Phase II: Found in Legacies from 2000+, Imprezas from 1999+, and Foresters from 1999+. Rated at 165hp and 166 ft-lbs. There was a slight compression ratio change from 1999-2000 where it went from 9.7:1 to 10.0:1.
USDM EJ20: US Domestic Market WRX. Found in 2002+ WRXs. Rated at 227hp and 217 ft-lbs. Turbocharged, intercooled, open deck, and decent heads.
EJ255 DOHC: Available in 2004 in the Forester XT. Rated at 210hp and 235 ft-lbs. Turbocharged, intercooled, VVTi (Variable Valve Timing), and drive by wire.
EJ257 STi DOHC: Available in 2004 in the WRX STi. Rated at 300hp and 300 ft-lbs. Turbocharged, intercooled, AVCS (Active Valve Control System), drive by wire, intercooler sprayer, and semi-closed design.

There is also a large variety of engines available from the JDM and EDM locales. The EG33 from the SVX and the EZ30 from the new H6 Legacy can also be found, but they are larger and will be more difficult to swap.

With that out of the way, the choices are pretty limitless. As stated previously, since these are all EJ series engines, they will all bolt into any Forester, Impreza, or Legacy. If the recipient car was an NA car and is receiving a turbo motor from a donor car, then swapping in a turbo crossmember is mandatory to clear the turbo up-pipe. A turbo crossmember from the 1990-1994 Legacy is a direct
swap into the old-age Imprezas. A turbo crossmember from a USDM WRX will require shims between the front control arm front bushing and the crossmember. http://forums.nasioc.com/forums/show...hreadid=351399

Q: "Where can I find miscellaneous parts needed for my project?"A: Unless it is JDM, you can find the parts both used and brand new. Some personal favorites of mine for used parts include http://www.4subarusuzukikiaparts.com, http://www.car-part.com, http://www.lkqcorp.com, and http://www.copartfinder.com. Sometimes, going new is the only way to go. If that is the case, there are a number of great dealerships registered as vendors on this site, http://www.subaruparts.com, or your local dealership. Most of the vendors registered here offer parts at near wholesale and actively watch the Private Wanted Classifieds. If you don't have a connection at the local dealership, they are probably going to charge you full retail price; retail is often $2 more for a $5 item and goes up from there. If it is JDM, then try some of the JDM importers such as those listed above. There are a few Japanese members on the board but please don't hound them to hit their local Subaru parts department for you.

Q: "Can I update my Impreza to look like a 2.5RS?"A: Yes, you can. The chassis has remained the same from 1993-2001. There have been very few drastic updates over the years. There was a facelift done in 1997, but it uses the same mounting points. The RS bumper was updated in 1999 to use the Version V bumper. This required a new bumper beam. The items needed can be found in this thread: http://forums.nasioc.com/forums/show...hreadid=390362

Q: "I'm doing an EJ20 swap, which exhaust should I use?"A: Until proven otherwise, the exhaust from a standard WRX from 1993-2004 has remained relatively unchanged. This means that if you are performing a swap from an Impreza chassis to an Impreza chassis, you can use any complete WRX exhaust. If you are swapping from an Impreza chassis to a Legacy chassis, then the exhaust must be lengthened to accomodate the longer chassis.

If you are doing a piece-meal exhaust, there are four types of downpipes available from any of the EJ20 equipped cars: the twin-turbo downpipe, a la GTB; the twin-scroll downpipe, a la STi Ver. VIII; the IHI flanged downpipe from a pre-MY01 JDM vehicle or post-MY01 non-JDM vehicle, a la USDM WRX or STi Ver. VI; or finally the IHI flanged downpipe from a post-MY01 JDM vehicle; a la STi Ver VII. The twin-turbo downpipe is only going to work in a RHD car, so this will almost never be used. The twin-scroll downpipe can only be used with an IHI twin-scroll turbo, so this will only be used with some STi Ver. VIII vehicles. The pre-MY01 JDM downpipe is the most common downpipe used with EJ20 vehicles. The post-MY01 JDM downpipe was introduced with the GG/GD chassis and is a few inches shorter than the pre-MY01 downpipe.

If you choose the pre-MY01, then you must mate it with a similar system. It can be mix-matched as long as it is not matched with a post-MY01 JDM system; this includes using cat-backs designed to work with the EJ25 engines. If you choose the post-MY01, then you must mate it with what is commonly referred to as a "JDM cat-back". The flange at the axle was rotated on the GG/GD chassis so the mid-pipe and the axle-back must be from the same chassis generation.

Q: "Do I have to do any wiring to swap <insert engine here> into my <insert Subaru here>?"A: It is hard to answer that with a blanket statement, but it is safe to say that most swaps are going to require rewiring.

Q: "So how hard can wiring really be?"A: The difficulty is all in your perception of things. If you are capable of reading wiring diagrams, handy with the soldering gun, and able to have your car down for about two weeks, then its not that difficult. Be prepared for headaches when you can't find what is causing that little quirk. Here is a preview of the things to address: http://forums.nasioc.com/forums/show...hreadid=345873. However, there are also companies who have a made a business doing these conversions so there is enough difficulty that it shouldn't be taken lightly.

Q: "I think I can do this wiring myself, but I will need some help. Where can I turn?"A: You can start off by searching this forum here. There are a lot of veterans out there that know a lot. Do a search first before asking a new question. Chances are, it has been asked before. You can also go to Subaru's very own technical information site, http://techinfo.subaru.com/html/index.jsp, or you can also try All Data: www.alldata.com.

Q: "Can I use <insert engine here> with <insert transmission here>?"A: The answer is almost a resounding yes. All EJ series engines share the same bolt pattern on the bellhousing. While some use fewer bolts than others, they will still bolt up.

One caution: the turbo transmissions use a pull-style clutch whereas the NA transmissions use a push-style clutch. If you are swapping transmission types, you need to match the transmission up with the correct clutch/flywheel assembly.

One more precaution: if you are swapping in a transmission, you need to be sure that your rear differential final drive ratio matches the final drive ratio of your transmissions. Installing a new transmission without checking this could permanently damage your center differential! Putting an engine from a FWD car into an AWD car or vice versa does not change the swap criteria as it will still all bolt together.

Thirdly, the older transmissions use a different shift linkage joint attaching to the shift forks of the transmission. The older transmissions have a fork that attaches to the rest of the shift linkage whereas the newer transmissions have a barrel joint. This must be updated if you are to change from an older tranny to a newer one or vice versa. It is believed that the older style shift linkage was used up until 1997. Beyond 1996, the transmission linkage should be the new style.

Finally, the older transmissions utilize a stud on the transmission for mounting the lower hole of the flange of the starter. If you swap in a newer transmission onto an older block, the block will not have the threads for the lower starter bolt. Some have reported success with just using the upper starter bolt, others have tapped a hole into the block.

Q: "Why can't I just swap in a new engine and leave everything else?"A: Good news, you can! The structure and strength of the transmission is realtively unchanged since the 1993 Imprezas (not necessarily a good thing). There are some exceptions though: the turbo Legacies had a more uniform metal composition in the gears while the new STi comes with a robust 6-speed. Other than that, the gear strength is almost the same. You can read all about this here: http://forums.nasioc.com/forums/show...hreadid=289335

Q: "I have a FWD Subaru, can I convert it to AWD?"A: As previously stated, Subarus are very interchangeable. If your car came with an EJ series engine, then any other engine components from an EJ series engine will drop into your chassis. Most of the time, you can't slowly convert to AWD; many of the components require the removal and/or installation of other components to work.

Q: "What components are needed to convert a FWD Subaru to AWD? Also read as 'Transmission swap technicalities'"A: A new transmission will be required. Along with the new transmission comes the front diff, center diff, and tailshaft. You must also get the corresponding driveline for the transmission (side note here, if you are merely swapping one AWD transmission for another the MT typically shares one driveline between all other MTs and the ATs share another driveline; the STi 6-speed uses an AT driveline). There are many rear diff options, and any of them can be used as long as the final drive matches the final drive of the rear diff of the donor car the transmission came from. Front axles should be interchangeable, but newer axles are thicker. CV strength has remained the same and are not a weak point. Rear open diffs can be found on most Subaru models. Rear LSD s came on some Legacy Turbos, Some SVXs, 2000-2001 2.5RSs, and 2002+ WRXs. While final drive ratios vary, the axle splines do not. Your diff choice governs which rear axles are to be used. You will either need rear axles from an open diff Legacy or GC/GF/GM Impreza for an open diff or rear LSD axles from a 2000-2001 Impreza 2.5RS (ask for axles from 05/2000+ to be safe) for a rear LSD. If you are converting from AT to MT or viceversa, you will need the corresponding ECU since the AT ECU expects a TCU signal. You can spoof it as some have done.

"What else is needed?" Along with the basic driveline components, you are going to need most of the rear suspension and mounts from the transmission back. This includes the transmission crossmember, rear diff crossmember (and all in between), AWD gastank with driveline hump, struts and springs, AWD knuckles, a plethora of bushings, with the possibility of lateral links, swaybar, and trailing arms also being needed. Your best bet is to find an entire donor car that can be stripped. If that is not an option, you will be, as beachbum has said, 'nickle-and-dimed to death'.

Q: "I'm swapping transmissions. What clutch and flywheel do I need to use?"A: The clutch and flywheel needed for your transmission swap are dictated by the transmission itself. If you are using a turbo transmission (commonly found in turbo Subarus like WRXs [non 6MT] and Legacy turbos) then you will need to use a pull-style clutch and corresponding flywheel. If you are using a transmission commonly found on a naturally aspirated Subaru, you will need to use a push-style clutch and flywheel.